The present invention relates to a method and apparatus for thin provisioning of RAID storage.
Thin provisioning of a storage system is known, typically there is a storage pool with a fixed real size that contains a volume that is presented to a host system. The volume has a virtual size and takes more of the pool's capacity as more data is written to the volume. The volume comprises storage capacity from one logical unit number (LUN) or from many LUNs. LUNs can be one or more RAID arrays having different RAID profiles. If the volume has many LUNs with different redundancies, then the volume's redundancy is that of the weakest redundancy RAID profile in use. If the volume is constrained to LUNs with a specific redundancy, then the volume cannot increase in size to use more pool storage capacity. Only a small number of drives are able to contribute to rebuilding data for the failed drive when several small RAID arrays are used.